Optical disc drives have been put into practical use in a range from audio CD to a CD-ROM, a CD-R/RW, and a DVD, and they have been applied to diversified fields and developments to achieve higher performance have been actively conducted. In particular, with rapid market expansion of personal computers, the percentage of optical disc drives that are built in personal computers has been increasing recently.
The configuration and the operation of an optical pick-up control portion in a conventional optical disc drive will now be described with reference to FIG. 8. Pick-up module 2 comprises spindle motor 3 to rotate optical disc 1, optical pick-up (hereinafter, referred to as PU) 4 to read an information signal from optical disc 1, and feed portion 6 to move carriage 5, on which PU 4 is mounted, in a radius direction of optical disc 1. A laser diode (not shown, and hereinafter, referred to as LD) serving as a light source of a laser beam is placed in PU 4, and is driven by laser driving portion 12. A laser beam is emitted to optical disc 1 from objective lens 14 by way of optical elements in PU 4, and reflection light therefrom is received at an optical sensor (not shown) in PU 4 again by way of objective lens 14 and the optical elements in PU4. Analog signal processing portion 8 generates a focus error signal and a tracking error signal on the basis of a signal output from the optical sensor in PU 4, and outputs these signals to servo processing portion 9.
The focus error signal is a signal indicating a shift in a focal point direction between a light beam spot emitted from objective lens 14 and a recording surface of optical disc 1. The tracking error signal is a signal indicating a shift in a radius direction between the light spot and information tracks on optical disc 1. Analog signal processing portion 8 also generates a lens position signal indicating relative locations of objective lens 14 and carriage 5, by extracting low-frequency components from the tracking error signal, and outputs the lens position signal to motor driving portion 10.
Servo processing portion 9 is formed in digital signal processing portion 11, and comprises an ON/OFF circuit, an arithmetic circuit, a filter circuit, an amplifier circuit, etc. It performs focus/tracking control on objective lens 14 to enable a light beam spot to follow information tracks on optical disc 1, and it further performs feed control to enable objective lens 14 to maintain nearly a neutral position, with the use of low-frequency components of the tracking error signal. Feed portion 6 comprises feed motor 7, a gear (not shown), a screw shaft (not shown), etc., and moves carriage 5 by rotating feed motor 7. In this instance, feed motor 7 outputs a feed motor pulse periodically. Controller 13 controls the overall servo portion configured as has been described.
During playback operations, PU 4 irradiates a laser beam to optical disc 1 at a low output, receives reflection light from optical disc 1 at the optical sensor, and outputs a playback signal corresponding to the received light to analog signal processing portion 8. And analog signal processing portion 8 further outputs the playback signal to digital signal processing portion 11.
Digital signal processing portion 11 comprises a data slicer, a data PLL circuit, a jitter measurement circuit, an error correction portion, a modulation/demodulation portion, a buffer memory, a laser control portion, etc., and transfers the playback signal to host computer 15 as valid data.
During recording operations, digital signal processing portion 11 modulates data sent from host computer 15, and sends a recording instruction from the laser control portion to laser driving portion 12. Laser driving portion 12 supplies the LD with a predetermined current, and records information in information tracks on optical disc 1 by causing the LD to emit light in pulses at a high output, for example, through a method referred to as a multi-pulse recording method. Controller 13 also controls the overall record and playback portion configured as has been described.
As the optical disc drive in recent years becomes thinner and lighter as well as compatible with a recordable DVD, heat generation in the LD serving as the light source of a laser beam and in a driver IC serving as laser driving portion 12 to drive the LD is being raised as a big issue. In other words, because an output of the LD for a recordable DVD is high in comparison with the LD for a CD-ROM and a CD-R/RW, a quantity of heat generation is large. The same can be said with respect to the driver IC. Further, in the case of an optical disc drive reduced in thickness and weight, a member, such as carriage 5, to hold the LD and the driver IC is also made thinner and lighter, and a heat capacity and a surface area are smaller than in those of a member in a conventional optical disc drive. Hence, the LD and the driver IC tend to reach high temperatures. Operations of the LD and the driver IC become unstable when they are heated above their respective rated compensation temperatures. They therefore may become uncontrollable and stop, and in the worst case, data recorded earlier may be broken. Otherwise, they have to be forced to stop. Examples in the arts are Japanese Patent Laid-Open Application No.H05-266489 and Japanese Patent Laid-Open Application No.2003-281733, etc.
The invention has an object to provide a recording method for an optical disc drive and an optical disc drive capable of preventing an LD serving as a light source of a laser beam and a driver IC serving as a laser driving portion from becoming uncontrollable as they are heated to high temperatures above their compensation temperatures due to own heat generation or the influences from ambient temperature, and thereby enabling recording to be continued in a stable manner without being interrupted or stopped until it ends.